diff --git a/src/validate.ts b/src/validate.ts
index f70d348..c10f355 100644
--- a/src/validate.ts
+++ b/src/validate.ts
@@ -53,8 +53,8 @@ export function validate(parse: {
     if (intersection.length === 0) {
       // the command's exactlyOne may or may not include itself, so we'll use Set to add + de-dupe
       throw new CLIError(`Exactly one of the following must be provided: ${[
-        ...new Set(...flag.exactlyOne || [], flag.name),
-      ].join(',')}`)
+        ...new Set(flag.exactlyOne?.map(flag => `--${flag}`)),
+      ].join(', ')}`)
     }
   }
 
diff --git a/test/parse.test.ts b/test/parse.test.ts
index 1e58265..148bbd4 100644
--- a/test/parse.test.ts
+++ b/test/parse.test.ts
@@ -719,11 +719,11 @@ See more help with --help`)
       expect(() => {
         parse([], {
           flags: {
-            foo: flags.string({exactlyOne: ['bar']}),
-            bar: flags.string({char: 'b', exactlyOne: ['foo']}),
+            foo: flags.string({exactlyOne: ['bar', 'foo']}),
+            bar: flags.string({char: 'b', exactlyOne: ['bar', 'foo']}),
           },
         })
-      }).to.throw()
+      }).to.throw('Exactly one of the following must be provided: --bar, --foo')
     })
 
     it('throws if multiple are set', () => {